The objective of this project is to elucidate the processes whereby proteins form unique native structures and function selectively in solution. Employing high field C-13 NMR (68 MHz), we have been able to resolve individual carboxyl and tyrosine carbon atom resonances in hen egg white (HEW) lysozyme and bovine ribonuclease A (RNase). A number of these resonances were assigned to individual amino acid carbon atoms or specific locations in the protein on the basis of their pH titration behavior as well as by comparison of native and selectively modified or species distinct protein. Additionally, we have recently initiated studies of the self-association (gelation) of deoxy hemoglobin S (HbS) in solution and in the intact erythrocyte using relatively low field (15MHz) solid state C-13 NMR techniques. These later studies should enable us to provide a direct assay of the gelation process and factors affecting it. Current and projected work includes: a) further studies of HbS gelation; b) C-13 studies of the proteins unfolding in RNase; c) high resolution studies of several new proteins (leukemic lysozyme, staphylococcus nuclease, and the human C-reactive protein). BIBLIOGRAPHIC REFERENCES: Shindo, H., Hayes, M.B., and Cohen, J.S.: NUM Titration Curves of Histidine Ring Protons. IX. A Direct Assignment of the Resonances of the Active Site Histidine Residues of Ribonuclease. J. Biol. Chem., 25, 2644-2647, 1976. Shindo, H., and Cohen, J.S.: NUM Titration Curves of Histidine Ring Protons. S. Ribonuclease S-Peptide and S-Protein, J. Biol. Chem., 25, 2648-2652, 1976.